The invention relates to an insertion coupling.
Such insertion couplings are used, for example, in vacuum lines in automotive construction, to produce a connection between a tubular insertion part which is provided with a circumferential retaining rib and a sleeve-like coupling body. The insertion part can be produced from plastic or metal and be the end of the line or the connecting piece on a housing. The coupling body is usually manufactured from plastic and mounted on a line, but can also be a component of a housing.
Insertion couplings of this type are characterized by a locking mechanism which is effective between the coupling body and the insertion part and is intended to be a sealing connection between the line elements to be coupled in each case. They are known in numerous forms, particular attention having been directed toward functional reliability and properties of manageability with regard to assembly.
DE 43 000 37 C1 discloses an insertion coupling of the type mentioned at the start in which the locking mechanism is formed between the coupling body and the insertion part by a part which can be displaced radially with respect to the main axis and is intended to engage behind a retaining rib of the insertion part.
Comparable insertion couplings are known from DE 197 22 842 C2, DE 10 2004 062 887 B3, EP 17 19 944 A2, US 2004/0189001 A1 and DE 10 1006 019 257 A1.
The disadvantage of these insertion couplings is that the coupling is composed of various parts, which results in high costs for the individual parts, complex assembly and a higher frequency of errors. Correct latching of the insertion part in the coupling body is not always completely visible from the outside in the above embodiments.
The insertion couplings must be assembled in two directions, so the complexity for automatic assembly is considerably increased.
A further insertion coupling is known for example from DE 44 13 346 C1, the locking mechanism of which is formed by a bushing which is inserted into the coupling body axially and can be displaced axially to a limited extent when in the inserted position. The bushing consists of a ring which is positioned in the sleeve base of the coupling body, from which ring four webs extend with parallel axes, uniformly distributed around the circumference and toward the open end of the coupling body, two of which webs bear mutually diametrically opposite latching hooks which are intended to interact with the retaining rib of the insertion part. All webs are provided radially on the outside with projections which are accommodated in recesses of the coupling body such that they can move axially to a limited extent, so that the bushing is gripped by means of two protrusions, which project out of the coupling body and are integrally formed on the outside of the webs which are not provided with latching hooks, and can be moved axially relative to the coupling body in order to release the coupling state of the insertion part with the coupling body.
The disadvantage of this insertion coupling is that correct latching is not visible from the outside. Furthermore, the bushing forms an effective surface for the seal which is formed by means of O-rings. Owing to the necessary axial displaceability of the bushing, the O-rings used are pushed into an axial end position when the insertion part is introduced and pushed into an opposite axial end position with internal pressure when the coupling is loaded according to its intended use. Dirt can penetrate from the outside into the front region through which the O-rings must pass. The O-rings execute this displacement every time the coupling state is released and induced so that there is the risk that the O-rings become twisted and/or dirt particles accumulate in the sealing regions during this movement, as a result of which reliable sealing is no longer provided. This can present a considerable problem, especially if the insertion coupling is used in fuel lines. A sealing check during series production when the coupling is assembled into a module is not possible, as the O-rings only assume their effective position once assembled.
Another insertion coupling is known from the document U.S. Pat. No. 6,517,120 B1 and consists of an insertion part, which bears a circumferential retaining rib, and a sleeve part which bears a locking element which is intended to latch with the retaining rib. The locking element is arranged on the end of a tab which extends in an arc-shaped manner around the longitudinal axis of the sleeve part and is integrally formed on the latter, and extends into a gap in the sleeve part. Inside this gap, integrally formed on the sleeve part, there are discrete protrusions which limit axial deflection of the tabs on both sides. A locking face is integrally formed laterally on the locking element which has an introduction slant, which locking face forms an extraction securing means in combination with a stop tab, which projects radially beyond this face on the outside and is integrally formed on the sleeve part, in the event of an axial load on the engaged state of the insertion coupling by limiting a radial deflection of the locking element. The locking element is furthermore provided with an actuation section which projects radially out of the structure of the insertion coupling. The construction of this insertion coupling, the sleeve part of which consists of two parts which are inserted one inside the other, becomes relatively complicated. Also, it cannot be established whether a satisfactory engaged state is present with just a visual inspection, at least not easily.